LAS or LAF – What is useful and when?
What exactly do we love so much about wood fires? Nowadays, family homes are built very airtight and insulated. Due to the design, it makes sense to supply the required combustion air for a fireplace from the outside.
For fireplaces that are independent of room air (e.g. gas fireplaces), the law provides for so-called LAS fireplaces. Wood fire stoves built by craftsmen are formally classified as room-air-dependent fireplaces. Of course, it also makes sense here to supply the combustion air from the outside via a closed duct system. As a rule, these heating inserts all have a corresponding connection pipe and have a corresponding tight design.
The counterpart to the LAS in the area of room-air dependent fireplaces are air-flue solid fuel (LAF) chimneys, they have an integrated air shaft in addition to the flue gas duct. This is thermally "separated" from the flue pipe and approved by the manufacturer for the combustion air supply. All room-air-dependent individual fireplaces may therefore be connected to such a system.
Air flue system for gas fireplaces
LAS is only available for tested room-air-independent fireplaces. The system unit consists, for example, of BRUNNER gas fireplaces with BRUNNER LAS (gas), whereby it is designed as a concentric, tight double pipe system. In the inner metal pipe the flue gases are led outside, combustion air flows through the outer pipe and is fed directly to the gas fireplace.
Thermal separation is not relevant with this version, as a gas fireplace comes up to temperature immediately. The gas insert and chimney form a certified system assembly . The BRUNNER LAS for gas fireplaces can be installed flexibly and also serves as a retrofit.
Air flue solid fuels (LAF) for wood stoves
In a LAF chimney for fireplaces with wood fuel, two pipes run parallel to each other, so to speak. The flue gas pipe and air shaft are located in the masonry chimney, a thermal separation is made. This means that no temperature can be transferred from the flue gas system to the air system. This separation is important for a wood fire stove, as sufficient negative pressure is needed for the chimney to "get going".
Where are LAS chimneys suitable?
The chimney sweep knows which LAS chimney system is suitable for the building or construction project. He can also clarify whether multiple occupancies are possible. The stove specialist trade can provide information about suitable stove models.
Conclusion
Air flue systems are a perfect and compact installation option for functional flue gas and combustion air ducting. In the case of room-air dependent wood fire stove, the combustion air duct can also be routed to the outside in the floor structure, via the cellar and through the outer wall. This way, the fireplace always gets enough oxygen for clean combustion and there is no lack of oxygen inside the room, which would negatively affect the living climate. For carefree fireplace or tiled stove enjoyment.
Always consult a specialist when making technical decisions. A chimney sweep or a specialist stove dealer can help you reliably and competently. You can find stove manufacturers on our homepage under Experience BRUNNER.
